<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width,initial-scale=1.0,maximum-scale=1.0,user-scalable=0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>textarea</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        body{
            width: 100%;
        }
        input, textarea{
            width: 60%;
            height: 40px;
            margin: 20px auto;
            display: block;
        }
    </style>
    <script src="./javascripts/jquery-3.1.1.js"></script>
</head>
<body>
    <input class="input" placeholder="请输入内容"/>
    <textarea id="t1" class="t" placeholder="展示内容"></textarea>
    <textarea id="t2" class="t" placeholder="展示内容"></textarea>
    <script>
        $(function(){
            $('.input').on('change', function(e){
                $("#t1").val($(this).val())
                $("#t1").html($(this).val())
            })
        })
    </script>
</body>
</html>